TERROR ON BOARD

Charles V. PenaTHE BALTIMORE SUN

On Christmas Day, alleged would-be terrorist Umar Farouk Abdulmutallab managed to light his pants on fire but, fortunately, not detonate what amounted to an underwear bomb aboard Northwest Airlines Flight 253. President Barack Obama said, "A systemic failure has occurred, and I consider that totally unacceptable," and he has ordered a full review of security procedures at airports.

But did the "system" really fail?

To begin, airport security passenger screening is designed primarily to identify and prevent people from bringing weapons on board a plane to avoid another hijacking similar to Sept 11, 2001.

Metal detectors and X-ray machines are not intended to detect explosives. Just as hijackers brought box cutters on board on Sept. 11 - when airport security was then focused on guns - Mr. Abdulmutallab appears to have exploited a loophole. It's simply unrealistic to expect security to have detected the pentaerythritol tetranitrate (PETN) hidden on his body.

To be sure, Mr. Abdulmutallab's purchase of a one-way ticket with cash and not having any luggage should have at least raised some eyebrows at the airport. But it's not certain that a secondary screen consisting of a cursory pat-down and inspection of his luggage would have found the PETN.

But wasn't Mr. Abdulmutallab on some sort of watch list? Shouldn't we have known he was a threat, especially since his father reported to the CIA that he was concerned about his son becoming radicalized? Hindsight is always perfect, so it's easy to say "yes." While it's clear our vast intelligence and Homeland Security apparatus could have done a better job communicating (such is the curse of bureaucracy), it's always easy to connect the dots backward from a known event.

Mr. Abdulmutallab's name on a watch list - which consists of more than 500,000 names even though there probably aren't that many terrorists in the world - didn't mean he was a verifiable terrorist threat. It simply meant that the government made a judgment that he might pose a risk, the operative word being "might."

It's a good bet that the watch list has more than few cases of mistaken identity - just as former U.S. Sen. Edward M. Kennedy was stopped and questioned at airports on the East Coast five times in March 2004 because his name appeared on the government's no-fly list. Moreover, just because someone is "radicalized" doesn't automatically mean they have embraced and are contemplating terrorism.

So the system "failed" only if we expect it to be prescient and believe all risk can be eliminated.

Nonetheless, all the angst has resulted in additional security. Since technology is not in place to screen passengers for explosives, people are being patted down and carry-on bags are being hand-inspected. But making passengers sit for the last hour of a flight is a useless measure that won't do anything to stop a terrorist who has smuggled explosives onto a plane.

So, where do we draw the line between security and liberty? Should we tolerate strip searches (or virtual strip searches via full body scans employed by the Dutch since the failed attack)? If so, what next? Body cavity searches?

Ultimately, what the "lap bomber" incident demonstrates is that there is no such thing as perfect security, and chasing it is a Quixotic quest. Just as police forces can't prevent all crime or catch all criminals, neither can homeland security avert all terrorism. Most importantly, just as we shouldn't sacrifice essential freedoms to fight crime - such as probable cause and the need for a search warrant - neither should we do so for the sake of security.

Charles V. Pe?a is a senior fellow with the Independent Institute and author of "Winning the Un-War: A New Strategy for the War on Terrorism." His e-mail is cpena@independent.org.